Pneumatic radial tire with side cut resistance

Abstract

A pneumatic radial tire, particularly for a construction vehicle, has a carcass ply arranged toroidally between a pair of bead cores, containing rubber coated steel cords disposed radially therein, being turned up around each bead core from the inside to the outside of the tire and the turn-up portion of which around each bead core extends to around 1/2 height of the tire height H. When the radical length of an overlapping portion of the turn-up portion of the carcass ply and the main carcass ply is h 1 and the thickness of the overlapping portion is w 1 within a range of ±0.1 H having half height H/2 of the tire height H as the center, the radial length h and the thickness w of a reinforcing rubber material arranged between the turn-up portion of the carcass ply and the main ply satisfy the following formulae (1) 0.2w 1 ≦w≦1.0w 1 , and (2) 0.5h 1 ≦h≦1.0h 1 , and said reinforcing rubber material satisfies the following conditions (3) 100 parts by weight of rubber includes 10-80 parts by weight of a cis-1,4 polybutadiene, and (4) a modulus of elasticity M is 60 kgf/cm 2 ≦M≦100 kgf/cm 2 at 300% elongation and a rebound resilience coefficient R is 0.4<R<0.7.

We claim: 
     
       1. A pneumatic radial tire comprising: at least one carcass ply arranged toroidally between a pair of bead cores, said at least one carcass ply containing rubber coated steel cords disposed radially therein and being turned up around each bead core from inside to outside of the tire, the carcass turn-up portion around each bead core extending to around one half height H/2 of a tire height H, wherein, when a radial length of an overlapping portion of the turn-up portion of the at least one carcass ply and a main portion of said at least one carcass ply is h 1  and a thickness of the overlapping portion is w 1  within a range of ±0.1 H having half height H/2 of the tire height H measured from a bead base line as the center, a radial length h and a thickness w of a reinforcing rubber material arranged between the turn-up portion of the at least one carcass ply and the main portion of said at least one carcass ply satisfy the following formulae (1) 0.2w 1  ≦w≦1.0w 1 , and   (2) 0.5h 1  ≦h≦1.0h 1 , and said reinforcing rubber material satisfies the following conditions     (3) 100 parts by weight of rubber includes 10-80 parts by weight of a cis-1,4 polybutadiene, and   (4) a modulus of elasticity M is 60 kgf/cm 2  ≦M≦100 kgf/cm 2  at 300% elongation and a rebound resilience coefficient R is 0.4<R<0.7   
     
     
       2. The pneumatic radial tire of claim 1, wherein: 0.3w 1  ≦w≦1.0w 1 .   
     
     
       3. The pneumatic radial tire of claim 1, wherein: 0.7h 1  ≦h≦1.0h 1 .   
     
     
       4. The pneumatic radial tire of claim 1, wherein said reinforcing rubber material has a length h of 0.9h 1  and a thickness w of 0.3w 1 . 
     
     
       5. The pneumatic radial tire of claim 1, wherein said reinforcing rubber material has a length h of 1.0h 1  and a thickness w of 1.0w 1 . 
     
     
       6. The pneumatic radial tire of claim 1, wherein the carcass rubber coated steel cords have a 1×3+9+15 construction. 
     
     
       7. The pneumatic radial tire of claim 1, further comprising a belt positioned radially outside said at least one carcass ply and comprising four layers having steel cords crossing each other at an angle of 23° with respect to an equatorial plane of the tire. 
     
     
       8. The pneumatic radial tire of claim 1, further comprising a belt positioned radially outside said at least one carcass ply and comprising two layers having steel cords of a (1+6)+6×(1+6) construction crossing each other and two layers having steel cords of a 3×7 construction crossing each other.